Diagnosis Tuber aztecorum is a sister species to T. castilloi, but T. castilloi differs by having larger spores, 27–63 × 20–40 μm, is without an irregular thickness to the cell wall on peridial hyphae and is associated mainly with Quercus spp. Also resembles T. guevarai but T. guevarai has narrow spores that are 18–55 × 16–42 μm and creamyellow fruiting bodies and rDNA variation.